I read a couple of comments to that effect on this Youtube video, which is basically a man ranting in Cockney from the movie Football Factory (2004). The comments bemoan American ignorance about the actual frequency of Cockney speakers, and suggest that it's all but disappeared amongst the working class except in a few areas. Saddening, if true. Is it? (I'm not looking for a thesis, just "man-on-the-street" type opinions.)

Well, 'I thought' means 'I heard it somewhere but have absolutely no evidence for it. So I googled it. They seem to be related but not identical. See Estuary English and Cockney. Re: another question, EE is non-rhotic and keeps 'th', where Cockney is rhotic and fronts 'th' to 'f'.
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MitchApr 12 '11 at 0:36

1

Also, not actually knowing anything but what I get from the internet, Jafaican seems to be more of a West-End black cool wannabe thing (Ali G) and Cockney is more of an East-ender white thing. So 'replaced' makes it sound like one population is changing dialects, but the reality looks like just that in the separate populations, there is more media attention to one rather than the other.
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MitchApr 12 '11 at 0:46

Look here me old china, the East End has basically gone to the dogs - lucky if you can find someone who speaks English, forget about Cockney.

Most punters who still speak Cockney live in Essex, Kent, with a few old school Cockney Yiddish folk in North London (Barnett, Golders Green). The old school 'real' cockney lived within the sounds of the Bow Bells and as I say you won't even hear many people speaking English round there now days, let alone a dialectical variation. It's all Pakistani and Bengladeshi in the East End nowadays.

Sadley me old mucker, successive British government have allowed many parts of the UK turn into a ten ounce rump (a dump). If you complain about it in public you'll be painted as an anachronistic pariah. I've had people in my cab from all over the world speak about it, they can't believe what they see. It's proper 'chicken oriental' (mental) mate.